Molecularly Imprinted Polymers for Cell Recognition

Since their conception 50 years ago, molecularly imprinted polymers (MIPs) have seen extensive development both in terms of synthetic routes and applications. Cells are perhaps the most challenging target for molecular imprinting. Although early work was based almost entirely around microprinting methods, recent developments have shifted towards epitope imprinting to generate MIP nanoparticles (NPs). Simultaneously, the development of techniques such as solid phase MIP synthesis has solved many historic issues of MIP production. This review briefly describes various approaches used in cell imprinting with a focus on applications of the created materials in imaging, drug delivery, diagnostics, and tissue engineering

Deposition of functionalized polymer layers in surface plasmon resonance immunosensors by in-situ polymerization in the evanescent wave field

Traditionally, the integration of sensing gel layers in surface plasmon resonance (SPR) is achieved via “bulk” methods, such as precipitation, spin- coating or in-situ polymerization onto the total surface of the sensor chip, combined with covalent attachment of the antibody or receptor to the gel surface. This is wasteful in terms of materials as the sensing only occurs at the point of resonance interrogated by the laser. By isolating the sensing materials (antibodies, enzymes, aptamers, polymers, MIPs, etc.) to this exact spot a more efficient use of these recognition elements will be achieved. Here we present a method for the in-situ formation of polymers, using the energy of the evanescent wave field on the surface of an SPR device, specifically localized at the point of interrogation. Using the photo-initiator couple of methylene blue (sensitizing dye) and sodium p-toluenesulfinate (reducing agent) we polymerized a mixture of N,N-methylene-bis-acrylamide and methacrylic acid in water at the focal point of SPR. No polymerization was seen in solution or at any other sites on the sensor surface. Varying parameters such as monomer concentration and exposure time allowed precise control over the polymer thickness (from 20–200 nm). Standard coupling with 1-ethyl-3-(3- dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide was used for the immobilization of protein G which was used to bind IgG in a typical biosensor format. This model system demonstrated the characteristic performance for this type of immunosensor, validating our deposition

Selection of imprinted nanoparticles by affinity chromatography

Soluble molecularly imprinted nanoparticles were synthesised via iniferter initiated polymerisation and separated by size via gel permeation chromatography. Subsequent fractionation of these particles by affinity chromatography allowed the separation of high affinity fractions from the mixture of nanoparticles. Fractions selected this way possess affinity similar to that of natural antibodies (Kd 6.6 × 10−8) M and were also able to discriminate between related functional analogues of the templ

Controlled release of the herbicide simazine from computationally designed molecularly imprinted polymers

The present study describes the development of materials suitable for environmental control of algae. Molecularly imprinted polymers (MIPs) were used as simazine carriers able to provide the controlled release of simazine into water. Three polymers were designed using computational modelling. The selection of methacrylic acid (MA) and hydroxyethyl methacrylate (HEM) as functional monomers was based on results obtained using the Leapfrog™ algorithm. A cross- linked polymer made without functional monomers was also prepared and tested as a control. The release of simazine from all three polymers was studied. It was shown that the presence of functional monomers is important for polymer affinity and for controlled release of herbicide. The speed of release of herbicide correlated with the calculated binding characteristics. The high-affinity MA- based polymer released 2% and the low-affinity HEM-based polymer released 27% of the template over 25 days. The kinetics of simazine release from HEM-based polymer show that total saturation of an aqueous environment could be achieved over a period of 3 weeks and this corresponds to the maximal simazine solubility in water. The possible use of these types of polymers in the field of controlled release is discuss

Development of electrochemical sensors for the detection of photosystem inhibiting herbicides

The objective of the present work is the development of an amperometric sensor for detection of hydrogen peroxide and its integration with spinach chloroplasts for the further development of a sensor for herbicides. The design of the sensor employed screen- printing electrodes which are easily produced at the facilities available in Cranfield University. The hydrogen peroxide sensor has been based on horseradish peroxidase (HRP) as the catalytic element and hydroquinone as the mediator. HRP has been immobilised onto the sensor surface using a newly developed thioacetale-based polymer capable of covalent immobilisation of primary amines. A new HRP-based biosensor was screen-printed using a carbon/polymer mixture. Hydrogen peroxide concentrations were analysed at the reduction potential of hydroquinone (–0.3 V). The biosensors developed in this work had low detection limit of HB2BOB2B (0.1 µM), long term stability (they can be stored for 2 months at 4 P 0 PC) and good reproducibility of measurements (RSD ~ 5%). The hydrogen peroxide sensor has been further integrated with spinach chloroplasts in an attempt to create a sensor for photosynthesis-inhibiting herbicides. It was found however that the quantity of HB2BOB2B generated by chloroplasts in our experimental conditions was not sufficient to allow quantitative analysis. Due to this we have developed an alternative approach based on the electrochemistry of the Hill reaction. In this reaction the photosynthetic process and electron flow passing through photosystem II (PSII) is monitored through the quantity of reduced artificial electron acceptor. Upon illumination of the chloroplasts a signal from a reduced acceptor or mediator was recorded chronoamperometrically. The added herbicide inhibits the photosynthetic process and decreases the reduction of mediator. The decrease in measured current which is proportional to herbicide concentrations have been used for herbicide detection. Three mediators of Hill reaction were tested including 2,6 dichlorophenolindophenol (DCPIP) duroquinone and potassium ferricyanide. The optimal results were obtained using DCPIP. The optimal wavelength for the excitation of chloroplasts was 650 nm. The chloroplasts have been immobilised onto the sensor surface using cross-linking with glutaraldehyde and bovine serum albumin. The developed system allowed reliable detection of herbicides (RSD = 10%) with a detection limit of 1-8 nM depending on the type of herbicide. The sensor can be stored for 3 months at -80 P 0 PC. Preliminary measurements of river water samples using this sensor were also performed indicating good correlation between the data obtained with GC-MS and the chloroplast-based biosensor developed in this study.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Substitution of antibodies and receptors with molecularly imprinted polymers in enzyme-linked and fluorescent assays

A new technique for coating microtitre plates with molecularly imprinted polymers (MIP), specific for low-molecular weight analytes (epinephrine, atrazine) and proteins is presented. Oxidative polymerization was performed in the presence of template; monomers: 3-aminophenylboronic acid, 3- thiopheneboronic acid and aniline were polymerized in water and the polymers were grafted onto the polystyrene surface of the microplates. It was found that this process results in the creation of synthetic materials with antibody-like binding properties. It was shown that the MIP-coated microplates are particularly useful for assay development. The high stability of the polymers and good reproducibility of the measurements make MIP coating an attractive alternative to conventional antibodies or receptors used in ELISA

The rational development of molecularly imprinted polymer-based sensors for protein detection.

The detection of specific proteins as biomarkers of disease, health status, environmental monitoring, food quality, control of fermenters and civil defence purposes means that biosensors for these targets will become increasingly more important. Among the technologies used for building specific recognition properties, molecularly imprinted polymers (MIPs) are attracting much attention. In this critical review we describe many methods used for imprinting recognition for protein targets in polymers and their incorporation with a number of transducer platforms with the aim of identifying the most promising approaches for the preparation of MIP-based protein sensors (277 references)

Attenuation of quorum sensing using computationally designed polymers

It is generally accepted that the majority of Gram-negative and Gram-positive bacteria communicate via production and sensing of small signal molecules, autoinducers. The ability of bacteria to sense their population density is termed quorum sensing (QS). Quorum sensing controls certain phenotypic traits, particularly virulence factors and biofilm formation. In this project a new solution for the attenuation of quorum sensing which involves selective sequestering of the signal molecules using rationally designed synthetic polymers was explored.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

The stabilisation of receptor structure in low cross-linked MIPs by an immobilised template

In molecularly imprinted polymers (MIPs) a high level of cross-linking is usually important for preserving the receptor structure. We propose here an alternative approach for stabilising binding sites, which involves the use of an immobilised template. The idea is based on the assumption that an immobilised template will ‘‘hold’’ polymeric chains and complementary functionalities together, preventing the collapsing of the binding sites. To test this postulate, a range of polymers was prepared using polymerisable (2,4-diamino-6- (methacryloyloxy)ethyl-1,3,5-triazine) and non-polymerisable (or extractable) (2,4-diamino-6-methyl-1,3,5-triazine) templates, methacrylic acid as functional monomer and ethylene glycol dimethacrylate as cross-linker. The level of cross- linking was varied from 12 to 80%. Polymerisations were performed in acetonitrile using UV initiation. Binding properties of the synthesised materials were characterised both by HPLC and equilibrium batch binding experiments followed by HPLC-MS or UV-visible detection. The adsorption isotherms of polymers were obtained and fitted to the Langmuir model to calculate dissociation constant, Kd, and concentration of binding sites for each material. The results strongly indicate that the presence of an immobilised template improves the affinity of MIPs containing low percentages of cross- linker. The low cross-linked MIPs synthesised with a polymerisable template also retain a reasonable degree of selectivity. Low crosslinked MIPs with such binding characteristics would be useful for the creation of new types of optical and electrochemical sensors, where induced fit or the ‘‘gate effect’’ could be used more effectively for generating and enhancin

New approach in multipurpose optical diagnostics : fluorescence based assay for simultaneous determination of physicochemical parameters

The development of sensors assays for comprehensive characterisation of biological samples and effective minimal-invasive diagnostics is highly prioritised. Last decade this research area has been actively developing due to possibility of simultaneous, real- time, in vivo detection and monitoring of diverse physicochemical parameters and analytes. The new approach which has been introduced in this thesis was to develop and examine an optical diagnostic assay consisting of a mixture of environmental-sensitive fluorescent dyes. The operating principle of the system has been inspired by electronic nose and tongue devices which combine nonspecific (or semispecific) sensing elements and chemometric techniques for multivariate data analysis. The performance of the optical assay was based on the analysis of the spectrum of selected dyes with discreet reading of their emission maxima. The variations in peaks intensities caused by environmental changes provided distinctive fluorescence patterns, which could be handled similar to the signals collected from nose/tongue devices. The analytical capability of the assay was engendered by changes in fluorescence signal of the dye mixture in response to changes in pH, temperature, ionic strength and the presence of oxygen. Further findings have also proved the ability of optical assay to estimate development phases and to discriminate between different strains of growing cell cultures as well as identify various gastrointestinal diseases in human. This novel fluorescence-based diagnostic tool offers a promising alternative to electrochemical systems providing high sensitive measurements with broad dynamic range, easy, inexpensive measurements and the possibility of remote sensing and extreme assay miniaturisation. Additionally it does not require reference signal. This new approach can impact on a number of applications such as routine minimal- invasive diagnostics for medical samples, biomedical analysis, pharmaceutical or cosmetic research, quality control and process monitoring of food or environmental samples.EThOS - Electronic Theses Online ServiceGBUnited Kingdo